This invention relates to a liquid pressure transfer method for applying a pattern for decoration to a loop-like member such as an annular member forming a closed loop like a steering wheel for an automobile or a U-shaped member forming an open loop like a chair back and a product decorated by the liquid pressure transfer method.
A steering wheel for an automobile has a core made of a metal material so as to exhibit strength at a predetermined level. The core is provided therearound with a grip surface section, which is formed of a material such as a plastic material, a wooden material, a leather material or the like which is selected depending on desired requirements, such as operability of the steering wheel, decorative characteristics thereof and the like. For example, a steering wheel provided thereon with a wooden surface section is evaluated as being a high-quality article, because it exhibits both satisfactory operability and decorative characteristics and requires considerable labor and time to manufacture. However, a recent tendency to reconsider casual use of natural materials in view of the need to protect the natural environment and the demand for reduction in manufacturing cost has lead to development of liquid pressure transfer techniques for substituting a plastic steering wheel material for a wooden steering wheel material and carrying out liquid pressure transfer of a woodgrain pattern for decoration on the plastic steering wheel material.
Application of a decorative pattern to a workpiece by liquid pressure transfer permits formation of a natural pattern which exhibits satisfactory conformability to a configuration of the workpiece, resulting in it being extensively practiced on a variety of workpieces. However, application of such liquid pressure transfer to, for example, a steering wheel encounters some important problems. A conventional steering wheel made of a wooden material is manufactured by subjecting two wooden rod-like materials which are semicircular in section to a treatment by moistening, heating and the like, to thereby bend them into an annular shape and then bonding them to each other while interposing a core therebetween. Thus, of course the wooden materials are each so arranged that a straight grain extends in a circumferential direction of the steering wheel. Such arrangement of the straight grain permits a user to have a sense of security and a sense of reliability.
The assignee proposed techniques for applying decoration to a steering wheel by liquid pressure transfer as disclosed in Japanese Patent Application Laid-Open Publication No. 329498/1998 entitled “A Method for Manufacturing a Steering Wheel to which Liquid Pressure Transfer Printing is Applied”. Unfortunately, the proposed techniques fail to exactly reproduce a straight grain pattern in a circumferential direction of the steering wheel or a longitudinal direction of a workpiece. Thus, in order to exactly reproduce a pattern of a natural material or the like on a workpiece having either an annular closed loop or a U-shaped open loop, it is required to transfer a transfer pattern to the workpiece without any distortion, therefore, further development on the liquid pressure transfer is still desired.